Threaded fastener removing tool

ABSTRACT

A tool for engaging a damaged or mutilated hexagonal socket in a threaded fastener, or the like, so that sufficient torque may be applied to the fastener to effect unthreading and removal thereof from a part with which the fastener is engaged. One end portion of the tool is tapered and hexagonal in cross section, thereby providing three pairs of opposite sides. Each side is tapered inwardly by a predetermined angle which permits the sides of the end portion to wedge against respective walls of the socket when forcefully driven therein. The opposite ones of each pair of sides of the end portion are spaced by a gauge width which, together with the taper of the sides, coact to prevent the end portion of the tool from bottoming in the socket when the tool is fully engaged in the socket.

This application is a continuation of application Ser. No. 483,542,filed Apr. 11, 1983 now abandoned.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a tool for removing a threaded fastener havinga damaged or multilated wrench receiving recess therein, and moreparticularly relates to a tool for removing cap screws, set screws, andother threaded devices having a damaged or mutilated,hexagonally-shaped, torque receiving recess therein.

(2) Description of the Prior Art

Various devices have been heretofore developed for effecting removal ofthreaded fasteners from a part or member with which the fastener wasengaged, either because a conventional tool could not apply sufficienttorque to the fastener to effect removal thereof or because the head ofthe fastener was damaged to the extent that a conventional tool couldnot properly engage the fastener. Examples of some tools which have beendeveloped for effecting the removal of screws having damaged heads aredisclosed in the Hilsinger U.S. Pat. No. 2,750,821 and Cummaro U.S. Pat.No. 2,815,054 patents. These devices were, however, complex inconstruction and difficult to use.

Devices have also been developed for removing broken or damaged studs.Examples of such devices are disclosed in the Murphree U.S. Pat. No.1,547,944 and Ferrell U.S. Pat. No. 1,604,032 patents. However, thelatter two devices required drilling of a hole in the damaged studbefore the removing tool could be engaged therewith to effectunthreading of the stud.

The problem of removing cap screws having hexagonal sockets in the headthereof has been particularly difficult whenever the socket in the headbecame damaged or mutilated to the extent that an appropriately sizedAllen wrench, or other torque applying tool, could not properly engageand transmit torque to the screw. A screw extracting tool ostensiblycapable of removing cap screws having hexagonally-shaped recesses in theheads thereof is disclosed in the Joyce U.S. Pat. No. 2,923,335.However, due to the high amount of torque required to effectdisengagement of cap screws or set screws which have been overtightened,rusted, or otherwise abnormally engaged with an associated part, theextracting tool disclosed in the Joyce U.S. Pat. No. 2,923,335, couldnot be relied upon to apply the degree of torque necessary to effectremoval of the screw.

SUMMARY OF THE INVENTION

Briefly described, in its broadest aspects, the present inventioncontemplates a tool for engaging a damaged or mutilated recess in athreaded fastener so that sufficient torque may be applied thereto toeffect removal of the fastener. In its more specific aspects, thepresent invention contemplates a tool which may be driven into a damagedor multilated hexagonal socket in a cap screw, set screw, or otherexternally or internally threaded device, so that sufficient torque maybe applied to the fastener, or other device, through the tool, tounthread the same from a part or member with which the fastener isthreadedly engaged.

The tool of the present invention, to be hereinafter described indetail, generally comprises an elongated tool body, having a tapered endportion that is adapted to be forcefully driven into a damaged ormutilated hexagonal recess or socket in the head of a fastener so thattorque can be applied to the fastener to effect removal thereof. Atleast the end portion of the tool is hexagonal in cross section so thatthe end portion has three pairs of opposite sides, each side beingtapered inwardly by an angle of between about 2 to 4 degrees withrespect to the axis of the body. In addition, the opposite sides of eachpair are spaced by a gauge width such that the sides will wedge againstthe walls of the recess in the fastener and before the end portionbottoms in the recess. The angle of taper of the sides of the endportion, and the gauge widths between each pair, is such as to limit thepenetration of the tapered end portion to between about 15 to 30 percentof the total depth of the recess when the end portion is fully wedged inthe recess.

Accordingly, it is a general object of the present invention to providea novel and improved tool that may be forcefully driven into a damagedor mutilated recess in a threaded fastener so that sufficient torque maythereafter be applied to the fastener through the tool to effectunthreading of the fastener.

A specific object is to provide a novel threaded fastener removing toolof the foregoing character, which is specifically adapted to engage andapply torque to a damaged or mutilated hexagonal socket in a cap screw,set screw, or the like, to effect unthreading thereof from an associatedpart.

Another object is to provide a novel and improved tool of the foregoingcharacter, which is simple in construction, reliable in operation, andeconomical to manufacture and maintain.

These and other objects and advantages of the invention will becomeapparent from the following detailed description and accompanying sheetof drawings, in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a tool for removing threaded fastenershaving a mutilated or otherwise damaged hexagonally-shaped recess orsocket therein which prevents removal of the fastener by a conventionalwrench;

FIGS. 2 and 3 are top and bottom plan views, respectively, of the toolillustrated in FIG. 1;

FIG. 4 is a vertical sectional view, with some parts in elevation,showing the approximate position of the tool illustrated in FIG. 1 whenoperatively engaged in the hexagonal socket of a cap screw;

FIG. 5 is a horizontal sectional view taken along the line 5--5 of FIG.4; and

FIG. 6 is an enlarged, fragmentary sectional view, with portions thereofin elevation, taken along the line 6--6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIGS. 1, 2, and 3, a threaded fastener removing tool, embodying thefeatures of the present invention, is illustrated and indicatedgenerally at 12. The tool 12, in the present instance, comprises anelongated tool body 13, which is preferably hexagonally-shaped in crosssection, and having an upper or impact receiving end 14 and a lower end16. The tool body 13 is preferably hexagonal in cross section, and thelower end 16 is smaller than the upper end 14.

According to the present invention, a portion 17 of the tool body 13,adjacent to the lower end 16, is tapered. Consequently, the tapered,lower end portion 17, which is also hexagonal in cross section, providesthree pairs of oppositely arranged sides, respectively indicated at22a,22b, 23a,23b, and 24a,24b. The tool body 13 may be of cold drawn41L42 annealed hexagon stock. However, the portion 17 is flame hardenedto a hardness of 55 to 58 on the Rockwell "c" scale.

Referring now to FIGS. 4 and 5 in conjunction with FIGS. 1, 2, and 3,the tool 12 is shown as it would appear when the lower or tapered endportion 17 is operatively engaged with the walls, respectively indicatedat 32a,32b, 33a,33b, and 34a,34b, of a hexagonally-shaped recess orsocket 36 in the head, indicated at 37, of a cap screw 38. The cap screw38 includes an externally threaded shank 39 which, in the presentinstance, is shown engaged with the internal threads, indicated at 40,in a member or part 41. The head 37 of the cap screw 38 is shown seatedin a recess 42 in a plate-like part 43, for example, which is held tothe part 41 by the head 37 of the cap screw 38.

Referring now to FIG. 6 in conjunction with FIGS. 4 and 5, and assumingthat the opposite pairs of walls 32a,33a, 33a,33b, and 34a,34b, of thesocket 36 have been damaged or mutilated so that the socket has enlargedto the extent that a conventional Allen wrench or other torque applyingdevice is unable to apply a sufficient amount of torque to the head 37to unthread the screw 38 from the part 41, the construction of the tool12 which permits removal of the damaged screw will now be described.

Thus, according to the present invention, at least one and preferablyeach of the three pairs 22a,22b, 23a,23b, and 24a,24b of the sides ofthe end portion 17 are inclined or tapered inwardly toward thelongitudinal axis, indicated at 46 in FIG. 4, of the tool body 17 by anangle of between about 2 to 4 degrees and preferably by an angle ofabout 3 degrees plus or minus 25 seconds. Such angle is indicated by theletter A in FIG. 6.

In addition to the foregoing inward taper, the sides 22a,22b, 23a,23b,and 24a,24b, of the end portion 17 of the tool body 13 are spaced fromeach other by a gauge width, indicated at d₁ in FIG. 6, which isnominally equal to the space between the upper edge, indicated at 47, ofeach opposite pair of the side walls 42a,42b, 43a,43b, and 44a,44b, ofthe socket 36 as initially formed and before damage or mutilationthereof. The axial location of the gauge width d₁ on the end portion 17is such that, when the end portion is forcefully driven into the damagedor mutilated socket 36, such as by one or more blows from a hammer, theportion 17 will penetrate the socket to a distance d₂ (FIG. 6), which isbetween about 15 to 30 percent of the total depth, indicated a d₃, ofthe socket 36. Preferably, the depth of penetration of the end portion17 is between 22 to 25 percent of the depth d₃ of the socket. Theaforementioned gauge width d₁, together with the aforementioned angularrange of taper of the sides 22a,22b, 23a,23b, and 24a,24b, assures thatthe tool 12 will wedge in the socket 36 and transfer a sufficient amountof torque from the tool to the screw 38 to effect removal thereof fromthe part 41 with which the screw is threadedly engaged. Since the head37 of the screw 38 is seated in the recess 42 in the part 43, as isusually the case, removal of the screw 38 without the tool 12 would bevery difficult.

It will be understood that the tool 12 will be made in different sizesso that, after determining the size of the socket 36 in the head 37 ofthe cap screw 38, for example, an appropriately sized tool is selectedfrom a set thereof which will achieve the required wedging action andpenetration of the end portion 17 in the socket 36 when the upper end 14of the tool is impacted into the socket.

After the end portion 17 of the tool 12 is firmly wedged in the damagedsocket 36 of the screw 38, torque may be applied to the tool body 13 inany convenient manner, such as by a box or open end wrench, or by apneumatically or electrically driven impact wrench, until the screwunthreads from the part 41. The screw 38 may then be easily removed fromthe end portion 17 of the tool 12 in any convenient manner, such as byclamping the body 13 of the tool 12 in the jaws of a vice and drivingthe screw 34 off of the end 17 of the tool with a hammer. The tool 12may then be reused as required.

It should be understood that while the tool 12 has been herein describedfor effecting unthreading of a cap screw having a mutilated hexagonalsocket, it could also be used to remove set screws or other types offasteners having hexagonal sockets which have been damaged or otherwiserendered incapable of receiving an appropriately sized Allen wrench orother similar type of torque applying tool.

While only one embodiment of the invention has been herein illustratedand described in detail, it will be understood that modifications andvariations thereof may be effected without departing from the spirit ofthe invention and the scope of the appended claims.

I claim:
 1. In combination, a threaded fastener engaged in a threadedopening in a part, said fastener having a head with a tool-receivingrecess therein, said recess having a hexagonal cross-section defined bythree pairs of opposite, generally parallel walls extending from anupper edge inwardly to a recess bottom portion, and a tool for removingsaid threaded fastener from said threaded opening when the recess in thefastener head is damaged or mutilated, said tool comprising:a generallyelongated tool body having opposite ends; a hexagonally shaped endportion tapering toward and terminating at said one end and receivablewithin said recess; said hexagonally shaped end portion having threepairs of opposite, converging sides; the opposite sides in each pairtapering inwardly at an angle between about 2 to 4 degrees with respectto the axis of said tool body; means on said sides of the hexagonallyshaped end portion, remote from said one end, for wedgedly engaging theupper edge of the recess when said one end is within the recess; and,the spacing of opposite sides of said hexagonally shaped end portionincludes a gauge width that is substantially equal to the distancebetween the upper edge of the wall of a standard size recess in saidfastener, and the axial location of said gauge width of said end portionis such that said one end of said tool body is positively spaced fromthe bottom of said recess when said gauge width is in substantialalignment with the upper edges of the walls of said recess.
 2. Thecombination of claim 1, in which the angle of taper of each of said toolbody sides is between about 3 degrees plus or minus 25 seconds.
 3. Atool for removing from a threaded opening a threaded fastener having ahead with a damaged or mutilated tool-receiving recess wherein saidrecess has a hexagonal cross-section defined by three pairs of opposite,generally parallel walls extending from an upper edge inwardly to arecess bottom portion, said tool comprising:a generally elongated toolbody having opposite ends; a hexagonally shaped end portion taperingtoward and terminating at said one end and receivable within saidrecess; said hexagonally shaped end portion having three pairs ofopposite, coverging sides; the opposite sides in each pair taperinginwardly at an angle between about 2 to 4 degrees with respect to theaxis of said tool body; means on said sides of the hexagonally shapedend portion, remote from said one end, for wedgedly engaging the upperedge of the recess when said one end is within the recess; and, thespacing of said opposite sides of said hexagonally shaped end portionincludes a gauge width that is substantially equal to the distancebetween the upper edge of the wall of a standard size recess in saidfastener, and the axial location of said gauge width of said end portionis such that said one end of said tool body is positively spaced fromthe bottom of said recess when said gauge width is in substantialalignment with the upper edge of the walls of said recess.
 4. The toolof claim 3, in which said angle of taper is about 3 degrees plus orminus 25 seconds.